Methods to detect and quantitate left ventricular dysfunction and myocardial ischemia provide a scientific basis for rehabilitation following myocardial infarction. Evaluation of these abnormalities by early postinfarction treadmill exercise testing has clarified prognosis and aided in establishing guidelines for vocational and avocational activity in our 225 uncomplicated patients. We propose to broaden these studies to include patients with more extensive ventricular dysfunction. We have five major objectives: 1) to use advanced radionuclide imaging techniques to characterize ventricular function and myocardial perfusion and to validate the ischemic nature of ST segment displacements on excercise and ambulatory electrocardiograms. 2) To evaluate the cardiovascular effects of bedrest and excercise training, utilizing new technology to quantitate long-term physical activity. 3) To utilize radioisotopic techniques to define "truly ischemic" responses to physical and environmental conditions within the laboratory and to use intra-arterial blood pressure measurements and computer analysis of ST segments of ambulatory electrocardiograms to confirm the ischemic nature of ST segment depression occurring outside the laboratory. 4) To compare standard clinical evaluation (resting ECG and X-ray, hospital course, history and physical examination) with functional evaluation (exercise testing, radioisotope imaging techniques and ambulatory electrocardiography) in the detection of mechanical, electrical and ischemic abnormalities soon after infarction and in the prediction of subsequent coronary events. 5) To compare the effect of focused rehabilitation, i.e., short-term counseling and home exercise training, with standard medically-supervised cardiac rehabilitation on medical and psychosocial status following infarction. Our purpose is to evaluate the efficacy of individual components of rehabilitation and to incorporate the most cost-effective of these into a widely available model program which is well integrated into standard medical care.